Mice experiments help scientists improve cancer vaccines

An additive used in anti-cancer vaccines is stopping them working properly, research in mice suggests. The latest findings contradict the previously-held belief that an oil in the vaccine mix boosts the immune response to the vaccine and could explain why so many human trials of the vaccines have failed.

The idea of an anti-cancer vaccine is to expose the body’s immune system to a tiny molecule typically found on the surface of a cancerous cell; the human body is then primed to attack any cells before they develop into tumours, and in some cases the immune system can even destroy pre-existing tumours. There have been more than 90 trials of such vaccines, some have worked but many have failed.

Cancer vaccines also often include a substance called IFA, short for "incomplete Freund's adjuvant", which are thought to stimulate an immune response. IFA is an oil so that it remain in the body to continue its work for longer.

Suspecting that this oil may be the reason behind so many failed trials, scientists studied its effect in mice. They found that immune cells accumulated at the site of the injected vaccine, and rather than spreading through the blood stream to the tumour, and many immune cells underwent “cell suicide” at that site. When the oily IFA was replaced with water or saline — substances easily processed by mice and men — the immune cells migrated to the tumours and began to destroy them.

The researchers now believe they may be able to improve the action of many existing vaccines by altering the additives used. They plan to conduct further research and could begin human trials later this year.